The present invention is concerned with the production of petroleum resins. In particular the invention is concerned with the discovery that particular catalysts are extremely active catalysts for the polymerization of a variety of resin feeds, including those feeds that are traditionally difficult to polymerize. The invention is particularly concerned with the improvement in the yield of resins and the reduction in unwanted or hazardous waste produced during resin production.
Petroleum resins are well known and are produced by the Friedel-Crafts polymerization of various feeds, which may be pure monomer feeds or refinery streams containing mixtures of various unsaturated materials. Generally speaking, the purer the feed the easier to polymerize. For example pure styrene, pure alpha methyl styrene and mixtures thereof are easier to polymerize than a C8/C9 refinery stream. Similarly, pure or concentrated piperylene is easier to polymerize than C4 to C6 refinery streams. These pure monomers are however more expensive to produce than the refinery streams which are often by-products of large volume refinery processes.
Hydrocarbon resins are used in adhesives, rubbers, hot-melt coatings, printing inks, paint, flooring, and other applications. The resins are usually used to modify other materials.
Aliphatic hydrocarbon resins can be prepared by cationic polymerization of a cracked petroleum feed containing C4, C5 and C6 paraffins, olefins, and diolefins also referred to as xe2x80x9cC5 monomersxe2x80x9d. These monomer streams are comprised of cationically polymerizable monomers such as butadiene, 1,3-pentadiene (piperylene) along with cyclopentene, pentene, 2-methyl-2-butene, 2-methyl-2-pentene, isoprene, cyclopentadiene, and dicyclopentadiene. In order to obtain these feeds the refinery streams are purified usually by both fractionation and treatment to remove impurities.
In addition to the reactive components, non-polymerizable components in the feed include saturated hydrocarbons that can be co-distilled with the unsaturated components such as pentane, cyclopentane, or 2-methyl pentane. This monomer feed can be co-polymerized with other C4 or C5 olefins or dimers. To date however, it has been necessary to purify the feeds to remove unsaturated materials that adversely affect the polymerization reaction or cause undesirable colours in the final resin (for example isoprene). This is generally accomplished by fractionation. To date polymerizations are catalysed using Friedel-Crafts polymerization catalysts such as unsupported Lewis acids (e.g., boron trifluoride (BF3), complexes of boron trifluoride, aluminium trichloride (AlCl3), or alkyl aluminium halides, particularly chloride).
Generally, C5 aliphatic hydrocarbon resins are synthesised using a piperylene concentrate stream that is obtained by fractionation to enrich the piperylene content and to reduce the content of olefins and diolefins that are more difficult to polymerize. The presence of these components in significant quantities (i.e. greater than 3 to about 5%) in polymerization feed blends is known to adversely affect the molecular weight and properties of the resin produced via cationic polymerization. However, obtaining these feedstocks has required expensive purification procedures. Therefore, there is a need in the art to provide a method of polymerising mixed feeds containing a variety of C4 to C6 olefins and diolefins into hydrocarbon resins without forming undesirable gels or very high molecular weight materials.
In our PCT Application WO 98/57999 we describe how raw feeds, which contain undesirable monomers, can be converted into hydrocarbon resins using traditional Friedel-Crafts catalysts providing a certain amount of aromatic olefin is added to the feed.
The process of WO 98/57999 however has several disadvantages. The Friedel-Crafts catalysts that have been used are typically aluminium based such as aluminium trichloride or boron based such as boron trifluoride. These homogenous catalysts suffer from the disadvantage that they become incorporated into the resin and must be removed by washing, which in turn produces hazardous waste water causing disposal problems. Furthermore, the catalysts themselves are hazardous and must be handled with care.
It has been suggested in PCT publication WO 95/26818 that supported Lewis acid catalysts may be used for hydrocarbon conversion reactions including the polymerization of unsaturated monomers such as piperylene. More recently, PCT publication WO 98/30587 is specifically concerned with supported metal halide catalysts (including aluminium trichloride) useful for the preparation of hydrocarbon resins from xe2x80x9cpurifiedxe2x80x9d monomer feeds. We have found, however, that the supported catalysts of this PCT publication are not sufficiently active and versatile to polymerize the feeds containing the variety of C4 to C6 olefins and diolefins found in refinery streams.
We have now developed improved supported halide based Lewis acid catalysts which are extremely active catalysts comparable to the heterogeneous unsupported catalysts in polymerising both the diverse and complex refinery feeds and pure feeds. Use of these catalysts also reduces the need for polymer purification and minimises waste disposal problems.